New laws designed to prevent a repeat of the Morecambe Bay cockling tragedy have come into force.
Morecambe Bay is a popular location for cockle-picking
At least 21 Chinese cocklers, all illegal immigrants, were swept away by rising tides in the Lancashire bay in February 2004.
Under the Gangmasters Licensing Act, everyone who supplies workers to the agricultural and food-processing industries must hold a licence.
Those without licences face up to 10 years in jail.
The Gangmasters Licensing Authority (GLA) started accepting licence applications in April.
Mike Wilson, chief executive of the GLA said: "It is simple to separate the legal operators who are licensed from the illegal operators who are not.
"There are no excuses for anybody in this industry to deal with the rogue operators."
"The GLA will start enforcing the new law immediately. We will use all means available to find illegal operators and prosecute them."
From 1 December it will also be an offence for anyone to use unlicensed gangmasters.
The Gangmasters Licensing Authority (GLA) said the definition of a gangmaster "includes traditional gangmasters and recruitment and employment agencies".